1. Field of the Invention
The invention relates to a vehicle running control system that creates a traveling path along which the vehicle is going to run, creates a speed pattern according to the traveling path, and controls running of the vehicle based on the traveling path and the speed pattern.
2. Description of the Related Art
A technology of creating the optimum traveling track of the vehicle and automatically running the vehicle using the traveling track has been developed. An example of the technology is described in a paper on “Numerical Analysis of Minimum-Time Cornering Method (Takehiko Fujioka, Daisuke. Emori: JSAE (Society of Automotive Engineers of Japan) papers, Vol. 24, No. 3, July 1993, p 106-p 111)”. This paper is concerned with a method of calculating an ideal track utilizing an optimization method, in which a length of time required to pass a corner is set as an evaluation function, and the ever-changing position and speed of the vehicle are calculated using the optimization method so that the evaluation function is minimized, so as to create a traveling track and a speed pattern which enable the vehicle to pass the corner in the minimum time.
In the technology of the above-identified paper, the position (track) and speed of the vehicle are changed, and evaluation functions are based on convergent calculations that are repeatedly performed while monitoring changes in the position and speed; therefore, when highly accurate traveling track and speed pattern of the vehicle are to be created, the number of calculations is increased, and the calculation time is prolonged. Therefore, a highly accurate, expensive control system needs to be installed on the vehicle.
Also, Japanese Patent Application Publication No. 2006-327545 (JP-A-2006-327545) discloses a system that sets sections for a target track (all of the sections) in a traveling plan of a mobile unit including a vehicle, and sets constraints to movement for each section, so as to improve a traveling result when the vehicle runs over all of the sections.
However, the system of JP-A-2006-327545 does not take account of how vehicle control based on a target speed pattern and driver's operations are coordinated, so as to make the actual speed pattern close to the target speed pattern, while meeting with the requested acceleration entered through the actual operation of the driver. Thus, there is room for improvement in coordinating vehicle control based on a traveling plan and driver's operations with further improved efficiency.
More specifically, typical examples of assist systems for improved fuel efficiency include, for example, “ECO MODE” of Toyota Motor Corporation, “ECON” of Honda Motor Co., Ltd., and “SI-DRIVE” of Fuji Heavy Industries Ltd. The respective systems of these companies are operable to change the accelerator pedal input in the form of depression of the accelerator pedal by the driver, by a moderate degree, for improvement in the fuel efficiency or fuel economy. Also, these systems are configured such that the driver makes a mode selection by means of, for example, a switch (SW).
However, these systems regard driver's operations as predominant inputs (true answers), and is not able to determine whether an input in the form of a driver's operation on the accelerator pedal or brake pedal is unnecessary or useless. In these systems, therefore, the inputs in the form of driver's operations are kept being predominant, and the control side provides only limited assistance for improvement of the fuel efficiency. Consequently, these systems can improve the fuel efficiency only by about 5% (a nominal value), and have difficulty in achieving a significant improvement in the fuel efficiency.